Oh Mandjas, so much of your note is familiar to me.
I look back way before *I* thought of the alcoholism and can still see signs pointing in that direction. There's a good chance she's been an alcoholic since the day I met her at 12, but I haven't made it that far back in therapy just yet. And honestly, it doesn't really matter to me at this point. The most important thing is dealing with the here and now.
I'm proud of you for writing your first letter. It was so difficult, I know. It will continue to hurt. I've stopped wondering about the harshness--but I did for some time. And the answer to that is NO. You are letting go with love --and that's the best you can do RIGHT NOW. It's important that you don't beat yourself up for the correct decisions that you make....otherwise you could teeter on a dangerous edge of codependency, in my opinion. You're doing the right thing, I promise. Regardless of her response (or lack of), you are STILL doing the right thing.
It's odd what you said about being engaged and pregnant because there are times when I've had issues with my health through the years and oddly, that's when my mother has been available to me the most. There's something about the alcoholic mother and needing to feel needed that I haven't quite put my finger on yet (or gotten to in therapy)....but they do seem to come out of the woodwork when there's something like that. So I know how you feel about the come and go type relationship, too. I would think "wow --she really is going to be present in my life" and then once it was over and I was perfectly healthy again ---bam, back to 'normal'. At least her normal.
You'll get there.....you're almost there. It's so very important, especially now that you have a child/ren (or a child on board --not sure of the time frame)--you can't let them be exposed to the same kind of alcoholic treatment you were exposed to.
Good for you!! Keep me posted on the letter.....the most important thing is that you wrote it. Period.